Regional Breath Sound Distribution Analysis in Single-lung Transplant Recipients

Background: Perfusion scintigraphy has been used to evaluate and monitor graft function in single-lung transplant recipients. In this study, our objective was to determine whether quantitatively measured regional breath sounds, using a computerized breath sound analysis device, correlate with the standard methods of monitoring graft function used at our facility for single-lung transplant patients. Methods: Quantitative regional breath sound measurements (QLD VRI) were performed with a VRIxp device on 37 single-lung transplant patients, who underwent perfusion scans and lung function testing for routine follow-up. The measurements were conducted on the same day. Results: Using a quantitative output based on objectively measured breath sounds, we established that there is good correlation (0.73) between QLD VRI and perfusion measurements for the grafted lung. Moreover, no significant differences were found between the two measurements (p = 0.898, t-test for paired data). In addition, the fraction of forced expiratory volume in 1 second (FEV₁; liters) of the graft lung was measured twice: once as a function of FEV₁ and regional perfusion and then as a function of FEV₁ and QLD VRI. High correlation (r = 0.88) and no significant differences (p = 0.72) were found between FEV_1tx (perfusion) and FEV_1tx (QLD VRI). Absolute error was 0.13 liter and the root-mean-square error (RMSE) was 0.17 liter. Conclusions: Objectively measured breath sound distribution in single-lung transplant patients can be readily quantified and correlated with graft function measurements. The method is quick and non-invasive and may provide useful information to aid clinicians in managing single-lung transplant patients.